1. Field
The disclosure relates to a copolymer, and more particularly to a polyimide copolymer and method for fabricating a patterned metal oxide layer.
2. Description of the Related Art
Polyimide (PI) has been widely applied in the semiconductor and display industries due to its thermal stability and excellent mechanical, electric and chemical-resistant properties. Polyimide is a thermosetting resin material. After a high-temperature (350° C. and above) process, it is very difficult to dissolve polyimide in usual solvents or amine strippers due to excellent chemical-resistance, restricting its applications. Therefore, the so-called soluble polyimide which forms a larger free volume between the molecules thereof through a specific molecular structure design to increase solubility has subsequently been developed. The soluble polyimide can still maintain its solubility under a 300° C. and below process temperature environment. However, during a high-temperature (350° C. and above) process, the molecular chains of the polyimide will mutually stack and tend to lower the energy and then shrink free volume which causes dramatic descent of solubility and results in insolubility.
Generally, during a metal oxide patterning process, a “lift-off” method is adopted to form metal oxide patterns, among others, although the soluble polyimide is widely used in the “lift-off” process, the process temperature must be limited to 350° C. and below. It is problematic if the soluble polyimide is used in a high-temperature metal oxide deposition process which requires 350° C. and above process temperatures. Therefore, development of a polyimide material which can still be dissolved in an organic solvent after a high-temperature (350° C. and above) process is required. Specifically, a temporary protective film capable of enduring high temperatures (350° C. and above) under metal oxide patterning processes, and finally, be removed using solvents to form metal oxide patterns is required.